Means for applying variable coatings to metal sheets



v R. B. McLlN Jan. 7, 1941.

MEANS FOR APPLYING VARIABLE COATINGS TO METAL SHEETS Filed Dec. 30, 1957INVENTOE /W% ATTORNEY lrp Patented Jan. 7, 1941 PATENT OFFICE MEANS FORAPPLYING VARIABLE COAT- INGS T METAL SHEETS Robert B. McLin, Follansbee,w. Va.

Application December 30, 1937, Serial No. 182,511 4 Claims. (01. 91-592)This invention relates to means for coating metal sheets with aprotective metal coating, and relates more particularly to apparatuswhereby one side of a metal sheet will have a thin metal 5 coating whilethe opposite side of the sheet will have a still thinner metal coating.

The economical value of producing such a variable coated sheet lies inthe ability of the apparatus to produce a metal sheet bearing anextremely li'ght coating of the protective metal on the side or surfacenot exposed to severe service, as, for instance, the outside of a sheetof tinplate to be made into cans, and a standard, or heavier, coating onthe opposite side of the sheet where its ultimate use requires anefficient protective coating.

I am aware that others have previously attempted to provide a sheet withcoatings of vary ing thicknesses on its opposite surfaces, but each hasresulted in a heavy coating on one side and a heavier coating on theother, as distinguished from my product wherein one side bears a lightstandard coating and the opposite side bears a coating lighter than thestandard coating. 2 In describing the invention in detail, reference isherein had to the accompanying drawing, in which the figure is avertical sectional view of a portion of a coating'machine used inconnection with the application of the metallic coating to the I 30sheets.

Referring to said drawing, the reference numeral Ill designates theframe or housing of a coating machine, which latter is adapted to beremovably mounted over and partially submerged 35 in a reservoir or pot(not shown) containing the metallic, coating, as molten tin, spelter,terne, or the like, on which floats the usual layer of oxidationpreventive oil, used also for smoothing the coating.

40 Journaled in appropriate bearings provided in the housing III are aseries of metal rolls I3 and I5, which govern the weight or thickness ofthe protective coating. As shown in the drawing, the rolls l3 and I5 aredisposed in pairs, each of 45 the rolls I3 being disposed opposite oneof the rolls l5. Each of the'rolls I3 is in vertical alignment with theother, and both of the rolls I5 are also vertically aligned. Aswill bemanifest, the roll arrangement may be of two, four, or six roll 50design and construction.

The rolls I5 are made of metal having a low carbon content, as, forinstance, .45% to 50% previous preparation a low carbon content. On theother hand, the rolls I3 consist'of metal having a high carbon contentof, for instance,- from 1.05% and up, and about 50 soleroscopichardness. As a consequence, the rolls l3 have dense, hard and smoothsurfacesdevoid of the small pits and pores and capable of taking a veryhigh polish, as is typical of this character of dense grain metal.

In practice, the sheet to be'coated is, after and pickling, passed i0through the flux box and metal pot where a quantity of the metal coatingis deposited on and adheres to all its exposed surfaces. As the sheetpasses through the coating bath, it contacts a guide l6 whereby thecourse of travel of the 1 sheet is directed upwardly between the seriesof pairs of rolls I3 and. I5.

The rolls I3 and I5, as they contact the sheets, function to removeexcess quantities of the metal coating and insure a uniform thicknessofsuch 20 coating. Inasmuch asthe surfaces of the rolls l3 are smooth,hard and dense, and devoid of surface indentations, porosity, andirregularities, the greater portion of the coating on the side of thesheet contacted by said rolls is removed, leaving but an extremely thinfilm of coating on this surface. On the other hand, the minute pits orpores present in the surfaces of the rolls I5 permit more of the coatingto adhere to the side or the sheet contacted by the rolls I5 and, as aconsequence, this side of the sheet receives a heavier coating than theopposite side, although neither of the surfaces is heavily coated.

Frictionally contacting the underside of one oreach of the rolls I3throughout the longitudinal extent thereof is an adjustable brush l8,preferably made of laminated asbestos and metal fabric or soapstone,such brushes functioning to wipe the metal coating from the roll withwhich it is associated and to maintain said roll free from eitherundesirable or excess coating metal, scrufi', or objectionableimpurities.

Suspended beneath the topmost roll I5, or, if desired, both rolls I5, isa trough l9 designed to contain a quantity of the coating metal.Obviously, the provision of this trough or troughs, and the additionalquantity of the coating metal through which the rolls l5 operate,increases the coating on that side of the sheet contacting the rolls 15.The trough is maintained filled with the metallic coating to the properlevel by ladling or pumping the same from the tin pot, and the metal inthe trough is prevented from oxidizing by reason of being locatedbeneath the oil level.

While the rolls l5 have herein been described as being made of highcarbon steel. it is also contemplated that these rolls may be made ofany of several alloy metals such as chromium,

nickel, tungsten, or any other material affording.

naled in said frame and disposed in opposing pairs, one of said rolls ofsaid pair being made of a metal having hard, dense grain characteristicsso as to present a surface devoid of surface irregularities, and theother differing metallurgically and being made of a metal having opengrain characteristics so as to present a roll having surfaceindentations.

2. In apparatus for use in applying a protective coating to metal sheetswherein one side of the sheet is to bear an extremely thin film of saidcoating and the opposite side of the sheet is to bear a coating heavierthan that borne by the first mentioned side of the sheet, said apparatuscomprising a frame, a series of rolls journaled' in said frame anddisposed in opposing pairs, one of said rolls of each pair being made ofa metal low in carbon content so as to afiord a roll surface havingminute indentations, and

the other of said rolls being made of a metal high in carbon content soas to afford a smooth roll surface substantially free of irregularity.

3. In apparatus for applying different thicknesses of protectivemetallic coating to the opposite sides of a metal sheet comprising aframe, a series of rolls journaled in the frame and disposed in opposingpairs, one of said rolls of each pair having a surface devoid of surfaceirregularities and the other roll of said pair having minuteirregularities in its surface.

4. In apparatus for use in applying a protective coating to metal sheetswherein one side of the sheet is to bear a thin film of said coatingsent a surface substantially devoid of surface irregularities, and theother roll differing metallurglcally and, being made of a metal havingopen grain characteristics so as to present a roll havingminuteindentations.

ROBERT B. MCLIN.

